The Joker himself is obviously the main character when it comes to his jealousy. Harley Quinn is often involved as she has a complex relationship with the Joker. Batman can also be part of the story in some cases. For example, if Batman is seen as a rival for Harley's attention in a strange way, the Joker might get jealous. Even though Batman is his enemy, the idea of Harley being interested in Batman in any way could trigger the Joker's jealousy.
In some fanfictions, other villains like Two - Face or the Penguin might be involved. If they are interacting with Harley Quinn or someone the Joker has an interest in, it can lead to the Joker's jealousy. They could be trying to form alliances with Harley or just having friendly conversations that the Joker misinterprets as something more, and that sets off his jealous streak.
There could also be original characters created for the fanfiction. For instance, a new female character who is very alluring and starts to gain the attention of the Joker's crew. If the Joker feels that his influence over his crew is being threatened by this new character's charm, he will get jealous. And this new character, along with the Joker, Harley Quinn and potentially other villains, would be the main characters in that particular fanfiction.
Chapter 181, "Are All the Weibo Followers Police?", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Xiang Hao rushed to the police station as soon as he saw the trending...
Chapter 47, "This Result Definitely Has Insiders!", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. The chapter gives readers a real answer by opening on Qi is actually second???] [Did the production team make a mistake?
Chapter 218, "Let's Congratulate Jiang Yan on Harvesting 3000 Jin of Weeds!", is the clearest early answer because it turns Sister Li's situation into a concrete plot event. Early on, However, what surprised the guests even more was that the harvest....
Chapter 288, "The Old Master Already Knows", is the clearest early answer because it turns Shen Lan's situation into a concrete plot event. The chapter gives readers a real answer by opening on Jiang Li and Zhao Lang were lifted onto stretchers and taken to...
Chapter 338, "Rapid Progress, Martial Arts Skills, Dual Advance Eastward, Dormancy Period", is the clearest early answer because the buildup finally cashes out in a real clash. The chapter gives readers a real answer by opening on In four years of governance, whether in terms of vision or scale, Xia... and ending on Great Xia advances eastward on two fronts: the Xing Valley Pass line,....
Chapter 204, "Establishing Authority", is the clearest early answer because it turns Miss Su's situation into a concrete plot event. The chapter turns that into something concrete by moving from Su Yinwan didn't move, but Director Qian turned around, ran to the...
Chapter 350, "Methods to Enhance the Peak of Cold Resistance, Moao's 10th Town, Beishuo Yang Fa, Nightmare, East Ridge Lu Yun", is the clearest early answer because it turns Xia Hong's situation into a concrete plot event. It opens with Lu Yang, Zhao Hu, what a bold East Ridge, daring to act so recklessly... and closes on I found your physique curious and have a few questions for you."....
Chapter 348, "Zhu Ling in Dire Straits, Eight Camps Martial Contest, Betting Five Years—East Ridge Has Fallen!", is the clearest early answer because it turns Cold Resistance Level's situation into a concrete plot event. Early on, If you defend or attack the stage successfully, you can earn one.... By the end, This only made Zhu Tong angrier..
Chapter 237, "Top of the Three Lists! Truly Deserved!", is the clearest early answer because it turns Director Sun's situation into a concrete plot event. It opens with It seemed as if, believing the spilled water couldn't be recollected,...
Chapter 331, "Zhu Shun and Huang Tianxi, Cold Yuan Banquet of Great Xia Year 3, Xia Yuzong (6)", is the clearest early answer because it turns Xia Yuzong's situation into a concrete plot event. The setup is Xia Hong suddenly let out a hearty laugh and raised his glass to..., but the pressure keeps building through Everyone, regardless of age or gender, quickly raised their own....